Imaging spectroscopy is defined as the combined analysis of both spatial and spectral information so that each picture element (pixel) in a two dimensional scene includes a third dimension of spectral information. This means that the spectrum of any pixel or group of pixels within an image can be measured. Digital Imaging Spectrophotometers/Spectroscopy (DIS) combine imaging spectroscopy with digital image processing techniques. DIS is a powerful screening tool which can be considered functionally equivalent to tens of thousands of spectrophotometers operating in parallel. DIS was developed for the rapid and noninvasive analysis of bacterial mutants directly on petri dishes.
The ColonyImager, is a low cost, user-friendly, high performance digital imaging spectrophotometer which has been redesigned and brought to market by KAIROS Scientific (Santa Clara, Calif.). This instrument supports spectral acquisition in both transmission and reflectance mode. In addition, fluorescence emission images can be acquired by selection of an appropriate long-pass filter. In order to obtain radiometrically calibrated spectra, one must correct for the wavelength response of the detector and optics. This has been successfully accomplished so that the quality of spectra is as good or better than that obtained from a double beam spectrophotometer. With 5 nm bandpass and data taken at 5 nm intervals, the ColonyImager can easily detect 2.5 nm spectral shifts. This is close to the limit imposed by a diffraction grating; therefore, conventional spectrophotometers are not much better in spectral resolution.
The first workstation based imaging spectrophotometer for analysis of petri plates was sold in 1991 and the PC based ColonyImager was brought to market in 1993, which also marked the first international sale of this device. This instrument has recently been featured in two technical articles and three scientific reviews, including a product review in Nature and a chapter in Methods in Enzymology. KAIROS is the sole source for this state-of-the-art equipment.